Z80 port map
| Number | Read | Write |
| $00 | Read sound code from 68k | Clear sound code buffer |
| $08 | NMI enable | |
| $04~$07 | YM2610 I/O | |
| $08 | Set $F000~$F7FF bank | |
| $09 | Set $E000~$EFFF bank | |
| $0A | Set $C000~$DFFF bank | |
| $0B | Set $8000~$BFFF bank | |
| $0C | Reply to 68k | |
| $18 | NMI disable | |